#include <queue>
#include <fstream>
#include <cstdlib>

using namespace std;

const int NMAX = 5000011;

int v[NMAX];
deque<int> dQ;

int main()
{
    int N, K, i;
    long long int sum;
    ifstream in("deque.in");
    ofstream out("deque.out");

    sum = 0;
    in >> N >> K;
    for(i = 1; i <= N; ++i)
    {
        in >> v[i];
        while(!dQ.empty() && v[dQ.back()] >= v[i]) dQ.pop_back();
        dQ.push_back(i);
        if(i >= K)
        {
            sum += v[dQ.front()];
        }
        if(i - dQ.front() == K - 1)
        {
            dQ.pop_front();
        }
    }
    out << sum << '\n';
}